Recent years have seen tremendous progress in the design and implementation of cryptographic proofs. In this talk I will survey a recent line of work that leverages tools from the PCP literature to achieve new constructions of zero knowledge succinct arguments, with improved efficiency and security against quantum adversaries. The practical potential of this new approach motivates a diverse set of theoretical questions that I will highlight.

Speaker: Raluca Ada Popa, UC Berkeley

Title: Oblix: An Efficient Oblivious Search Index

Abstract:

Search indices are fundamental building blocks of many systems, so much work has attempted to enable search on encrypted data to protect the confidentiality of the data. Unfortunately, practical schemes achieve efficiency at the expense of security, because they reveal access patterns to the encrypted data.

In this talk, I will describe Oblix, a search index for encrypted data that is oblivious (provably hides access patterns), is dynamic (supports inserts and deletes), and importantly, has good efficiency. Oblix relies on a combination of novel oblivious-access techniques and recent hardware enclave platforms (e.g., Intel SGX). In particular, a key technical contribution is the design and implementation of doubly-oblivious data structures, in which the client’s accesses to its internal memory are oblivious, in addition to accesses to its external memory at the server. These algorithms are motivated by hardware enclaves like SGX, which leak access patterns to both internal and external memory.

We demonstrate the usefulness of Oblix in two real-world applications: private contact discovery for Signal and private retrieval of public keys for Key Transparency.